Emperor Hirohito announced the surrender of Japan by radio message at noon on
August 15, 1945. At about 7 p.m. on the following day, several huge explosions
at the Navy's shinyō explosive motorboat base in Yasu Town (now part of Kōnan
City) of Kōchi Prefecture killed 111 men (including 23 shinyō crewmen) in the
128th Shinyō Special Attack Squadron and
wounded many others.
The book Kuroshio no natsu: Saigo no shinyō tokkō (Kuroshio summer:
Last shinyō special attack), published in 2009 more than 60 years after the
event, investigates in detail the following questions: Why did the accident
occur at Yasu? What was the source of a report that the enemy fleet was heading
north toward the Japanese main island of Shikoku? Why did the young shinyō boat
crewmen prepare to sortie? This historical study on a little known
incident delves deeply to find the answers to these questions, but ultimately
many uncertainties remain about what exactly happened and what led up to the
accident.

The author Eidai Hayashi interviews many Shinyō Special Attack Corps
survivors and other accident eyewitnesses in his search for answers to what
happened at Tei Base in Yasu Town. The interviewees include several Japanese Navy veterans who served
at shinyō bases other than Tei Base. He also consulted numerous
written sources in his research as evidenced by about 50 works listed in the
bibliography. Hayashi has authored many books related to Japan's wars and former
colonies such as Taiwan and Korea, and he is the recipient of several literary
awards. His prior publications include two well-researched books about Japan's
tokkōtai (Special Attack Forces): Jūbaku tokkō sakuradan ki (Heavy
bomber Sakura-dan special attack plane) (2005) and Rikugun tokkō shinbu ryō: Seikansha no
shūyō shisetsu (Army special attack Shinbu barracks:
Detention facility for survivors) (2007).

The author in the beginning does not clearly lay out either the book's purpose and
scope or the methods he used to obtain information, but the book cover gives
the main questions he tries to answer in the book. However, even despite these
main questions, some parts of the book seem to have little relationship with the
explosions at Tei Base that killed 111 men. However, most of these parts not
related to Tei Base will appeal to someone interested in Japan's Shinyō Corps as
Hayashi covers details of other shinyō bases located in Kochi Prefecture.

A two-page insert in front has historical photos of the plywood shinyō boat,
which had a one-man Model 1 and a two-man Model 5. The shinyō boat was powered
by a truck engine, and it carried 250 kg of explosives in its bow. The boats were
suicide (special attack) weapons in which crewmen lost their lives as the boats
exploded when hitting enemy ships. The book includes over 30 other photos
of shinyō squadron members, current locations of the shinyō bases, and other
subjects.

Toyoji Kunita, former 128th Shinyō Squadron member who received
serious injuries from fire at Tei Base in Yasu Town. Author Eidai Hayashi
could not interview Kunita since he had passed away before the start of the
research.

The book's contents are organized clearly into six chapters with each chapter
divided into several parts. After an Introduction that gives a background on
shinyō bases in Kochi Prefecture and a summary of the accidental explosions at
Tei Base in Yasu Town on August 16, 1945, Chapter 1 presents the shinyō special
attack weapon and general background on shinyō crewmen. Almost all crewmen
received their training at Kawatana Torpedo Boat Training School in Nagasaki
Prefecture. The young men selected to become shinyō crewmen were
almost all aspiring aircraft crewmen of 17 and 18 years of age in the Navy's Yokaren
(Preparatory Flight Training Program) at Tsuchiura Air Base and Mie Air Base.

Chapter 2 introduces several shinyō bases that were established in Kōchi
Prefecture on the Japanese main island of Shikoku. Each squadron with about 150
to 200 men was assigned to a single base along the coast. Each squadron had
either about 50 Model 1 one-man shinyō boats or about 25 Model 5 two-man shinyō
boats, so the number of shinyō crewmen totaled about 50 for each squadron. In
addition to the 128th Shinyō Squadron at Tei Base in Yasu Town, this chapter and
the rest of the book covers in some detail the following squadrons: 49th Shinyō
Squadron at Nomi Base, 50th Shinyō Squadron at Usa Base, 127th Shinyō Squadron
at Urato Base, 132nd Shinyō Squadron at Koe Base, and 134th Shinyō Squadron at
Kashiwajima Base. Tunnels were dug in the rocky hills and cliffs surrounding the
bay where each squadron was located in order to hide the shinyō motorboats from
detection and attack. The chapter provides maps of the different shinyō bases
that show the location of the tunnels. There is also a detailed
explanation of the organizational structure of the shinyō bases, since this has
importance in trying to understand the source of miscommunications that took
place on the day of the explosions at Tei Base. The Kure Naval District's 8th Tokkō (Special Attack) Sentai based
at
Saeki in Oita Prefecture included two Totsugeki Units based in Kōchi Prefecture:
the 21st with headquarters in Sukumo and the 23rd at Susaki Bay. Tei Base, along
with bases at Nomi, Usa, Urato, and Muroto, were part of the 23rd Totsugeki Unit
in the northern part of Kōchi Prefecture. The 21st Totsugeki Unit included
shinyō bases in the southern part of the prefecture and also included some bases
in Ehime Prefecture. The 128th Shinyō Squadron at Tei Base had 171 total members
including 7 officers, 48 crewmen, 31 maintenance workers, 14 headquarters
personnel, and 71 other base workers.

Chapter 3 discusses the situation with the various shinyō squadrons in Kōchi
Prefecture after the Emperor's announcement of surrender on August 15, 1945.
Orders came from the 23rd Totsugeki Unit headquarters for the squadrons to be
ready to sortie against enemy ships, since there was still a fear that the
mainland could be subject to an imminent enemy attack. The five squadrons in the
21st Totsugeki Unit are thought to have been in much the same situation as they
were ready to sortie in their shinyō motorboats whenever an order would come.
The young crewmen had been ready to die in shinyō boat attacks when the
Emperor's radio message of surrender was heard. Many of them at various bases
after drinking that night made comments among themselves that they still wanted
to sortie in order to make suicide attacks. The officers at Koe Base had to order crewmen
of the 132nd Shinyō Squadron in Tosashimizu to halt such plans to sortie as a group and remain
on alert to be ready to sortie if orders were given.

Chapters 4 and 5 represent the heart of the book where Hayashi addresses
the questions posed on the book cover. Chapter 4 starts with the official
account of the accident as published in the Yasu Town History, which states that
during the afternoon of August 16 an order by telegraph arrived: "The enemy
task force is heading toward Tosa to land on the home islands, so immediately
make preparations to sortie." All squadron members took their boats from the
tunnels and lined them up along the shore, but when the engines were being
adjusted, spilled gasoline suddenly ignited and one of the boats burned up.
Orders were given for the men to take cover. There were attempts to put out the
fires and to return to the boats after a few minutes when it seemed safer, but
the boat fuel tanks overheated and caused huge explosions. This accident
destroyed 23 of the squadron's 25 Model 5 two-man shinyō motorboats, and 111 men
died along with many injured. Hayashi then summarizes the results of several
personal interviews of the few squadron survivors and other eyewitnesses still
living. The eyewitnesses have some discrepancies between their stories, but they
talk mostly consistently of multiple explosions, the smell of gasoline in the
air, and running to a nearby tunnel to take cover. The author repeats several
times in the book that the Navy never conducted an official inquiry as to what
happened at Tei Base, which probably was due to the state of confusion that
existed within the Navy right after cessation of hostilities. The two survivors
who knew the cause of the fire before the explosions had both passed away by the
time that Hayashi started his research on the shinyō boat accident at Tei Base,
so it appears that the cause can never be known with certainty.

Shigeo Nagoya, former 128th Shinyō Squadron
member who drove men seriously wounded in Tei Base explosions to the
Japanese Red Cross Hospital in Kōchi City.

Chapter 5 presents several different incorrect reports related to the
accidental explosions at Tei Base. One was the supposed sighting of the
enemy fleet, but the original source of this report is not clear, and naval
reconnaissance flights from Kōchi Air Base did not confirm this sighting. Another false report
indicated that the masts of 13 enemy warships, which appeared to be cruisers, had
been sighted 25 kilometers south of Kōchi City. This message came by urgent
telegraph from Kochi Naval Air Group to the 23rd Totsugeki Unit headquarters
in Susaki before 6 p.m. on August 16, 1945. Therefore, when pillars of fire were
sighted in the direction of Yasu Town, the 127th Shinyō Squadron members at
Urato Base initially thought in
error that
the enemy bombardment had begun and that their shinyō motorboats would sortie
soon to attack enemy ships off Shikoku
Island. In another incident, the 134th Shinyō Squadron at Kashiwajima Base along
with the 21st Totsugeki Unit in Sukumo did not clearly understand the Emperor's
message of surrender, so they remained ready to sortie. Coincidently, an accident
similar to the one at Tei Base occurred at Kashiwajima Base at about the same
time. Gasoline apparently caught
fire at Kashiwajima Base and led to an explosion in one of the tunnels, but this accident destroyed
only three shinyō boats and slightly injured one person in comparison to the Tei
Base accident with 111 men killed, many injured, and 23 boats destroyed. This
chapter also goes into theories behind the mysterious disappearance of
Lieutenant Junior Grade Seisaku Takenaka, commander of the 128th Shinyō
Squadron, during and after the explosions at Tei Base, but a definitive
conclusion is never reached, although we know from the book's last chapter that
he was not injured and returned home to Ōsaka soon after the incident.

Chapter 6 covers the repatriation of shinyō squadron members. Parents who
heard the news of their sons' deaths had a difficult time in understanding why
they were killed in such an accident when the Emperor already had declared an
end to the war on the previous day. Each year there is an annual memorial
service at Yasu on August 16 to remember the 111 men who lost their lives in the
accidental explosions. A monument was erected on the former base site on August 16, 1956,
but Hayashi points out that the history engraved on the monument contains
several mistakes. For example, the monument states that 111 men of the 9th
Shinyō Squadron lost their lives on August 16, 1945, but actually the correct
squadron is the 128th Shinyō Squadron. Apparently the person who wrote the
history for the monument mistakenly picked up "9th" from the 9th group of
shinyō
squadrons formed at Kawatana Torpedo Boat Training School. Squadron leader
Seisaku Takenaka had the rank of Lieutenant Junior Grade, but the monument
history incorrectly states his rank as Lieutenant.

This thoroughly researched book demonstrates how difficult it can be to
conclude with any degree of certainty what happened exactly in a specific
historical incident, especially when most of the eyewitnesses have passed away.